After the downfall of Oster and his own dismissal from the Abwehr Canaris had lost all contact with the leaders of the military resistance. Early July 1944 he was informed about the intended attack on Adolf Hitler by Claus Schenk Graf Von Stauffenberg (Bio Von Stauffenberg). He was not involved in the organisation itself however and he was unaware of the detailed planning of the coup. The new resistance members labeled him as being too conservative and too careful. As late as the afternoon of July 20th , 1944, he was informed that the attempt had taken place. Canaris saw almost immediately that Operation Valkyrie (Fall Walküre, the code name of the operation), was doomed to fail. A little after 18:00 he therefore offered his congratulations to Hitler for surviving the bomb attack. He also destroyed all incriminating material linking him to the resistance. In doing so, he hoped to evade prosecution.
During the investigation that was launched after the attempted murder and which was being directed by Gestapo chief Heinrich Müller, Canaris’ name soon popped up. On July 23rd , 1944, he was arrested by the chief of the Amt Ausland of the SD, Walter Schellenberg personally. After his arrest he was interned in the school of the Grenz-polizei (border police) in Fürstenberg. He was treated rather well there.
After Hans Oster, who had been arrested as well, had mentioned his name during an interrogation, Canaris was transferred to the R.S.H.A. prison in the Prinz Albrechtstrasse however. Here he was subjected to lengthy interrogations and the tough prison life. Canaris however was able to withstand the interrogations rather well. He managed to confuse his interrogators by insinuations and with lots of information which in the end appeared to be useless.
On September 22nd the Gestapo found, on indications by a snitch, the archives that had been kept by Von Dohnanyi and which strangely enough had never been destroyed. These documents contained data kept by Dohnanyi about the attempts for a coup in 1938 – 1940. They also found a number of copies of the diaries of Canaris in these archives. Canaris was adamant that he had only been indirectly involved in the plots and was able to provide an acceptable explanation of his actions. Despite many interrogations and torture – his prison rations were lowered to 1/3rd of the already meager quantity and he was hardly granted any sleep – he refused to confess. His interrogators gave up for the time being.
On February 5th , 1945, Canaris was transferred to concentration camp Flossenburg, together with a number of other conspirators. The freshly arrived prisoners were confined to the bunker in the camp, which was intended for special prisoners only. Müller ordered the suspects to be kept in irons at all times and not be allowed to have any contact with the outside world. Canaris is said to have been rather optimistic in these days. He presumed he would survive the downfall of the Third Reich and that he would be liberated by the Allies. However this did not happen.Execution
Just one month before the end of the war, and very unfortunate for Canaris, an officer discovered his diaries by accident in a safe in the abandoned office of the Abwehr in Sossen, and notes on his trips to the front to win army commanders over to the coup against the regime. Up until that moment the RSHA had abstained from prosecuting the group around Canaris, as his involvement and that of the Abwehr in the coup against Hitler’s regime had been considered small and insignificant. However, with evidence of their conspiracy out in the open, an outraged Hitler ordered the execution of Wilhelm Canaris, Hans Oster, Hans von Dohnanyi (the most important conspirators within the Abwehr) and the reverend Dietrich Bonhoeffer who had also been involved in the plot.
Without a proper trial Wilhelm Canaris, Hans Oster, Karl Sack, Dietrich Bonhoeffer and Ludwig Gehre were sentenced to death on April 8th , 1945. The court consisted of SS members only; as an officer Canaris could only have been tried by a military court martial. After the verdict Canaris communicated briefly by means of knocking signals with a fellow prisoner, a Danish intelligence officer, who was locked up in the adjacent cell and who was to survive the war. His last words were: "Broken nose at last interrogation. My time is over. Was no traitor to my country. Have done my duty as a German. If you survive, send greetings to my wife." The statement: " Broken nose at last interrogation" Canaris most likely intended as a matter of speech, in reality that had not happened.)
The five condemned men were hanged in the early morning hours of Monday 9 April, 1945 in concentration camp Flossenburg. In order to humiliate them they were taken to the gallows naked. After the executions the SS members received a little bonus for their dirty work in the form of a schnapps and blood sausage. The bodies of the men were burned in the crematorium of the camp that same afternoon.